Recent reports have offered evidence that stress and emotion can alter measures of human cell-mediated immunity (CMI). In a previously reported study, Licke, et al., noted that life change stress (LCS) was associated with relative diminutions in natural killer cell activity (NKCA), a measure of lymphocyte cytotoxicity, in subjects who tolerated stress poorly. The goal of the present study is to determine if these results are replicable using improved psychometric measures, repeated NKCA determinations and possibly other measures of humoral and CMI. One hundred healthy male volunteers, ages 21-60, will be recruited. Subjects will undergo quantitative psychometric assessments of LCS, personality, mood, psychiatric symptoms, and social adjustment. On 3 occasions, each 3 months apart, a 100 cc blood sample will be collected and cryopreserved. Dependent variables will be NKCA and possibly other measures of cell-mediated immune function. NKCA will be assayed by the same laboratory used for the previous study. Results will be analyzed using correlations, one-way and two-way analyses of variance to examine possible independent or interactive effects of LCS and social adjustment, personality, mood and psychiatric symptoms on NKCA. If results again demonstrate that stress and psychosocial factors can influence human CMI, it will be further evidence that brain and behavior can alter cellular immunity. Such findings have significance for many fields of medicine.